How can I check batteries are fully charged?

[dmr]

The op is an off grid CCer (liveaboard). Assuming his batteries are half decent flooded lead acids then charging at 14.5v is just not good enough, simple as that. In the cold weather about 15v might be more appropriate.

 

................Dave

[WotEver]

The op is an off grid CCer (liveaboard). Assuming his batteries are half decent flooded lead acids then charging at 14.5v is just not good enough, simple as that. In the cold weather about 15v might be more appropriate.

 

................Dave

Which explains the sulphation/unequal cells.

 

Maybe AGM batteries. We live onboard full time so need things to work. I'm prepared to charge well every day and use the generator and charger regularly too.

Yes, AGMs might be a better fit for you with your low charging voltages. They can give excellent service but must be regularly fully charged as you describe because they cannot be equalised.

[nicknorman]

We don't live on our boat but do use it quite a bit. When not used, it is on shore power via the Mastervolt Combi, in other words the batteries definitely get fully charged. Despite that I found that after 6 months after fitting new leisure batteries the capacity had fallen way off to about 1/2 and needed an equalise to restore. 6 months for us is probably about the same as 6 weeks for you, in terms of cycles. Those batteries eventually died after 2 years (of leisure use) and that is why we now have Trojans.

 

As for the Victron and equalise mode, it probably depends on exactly which model you have. I don't have one but I seem to recall you can get it into equalise mode by judicious use of the on off switch. Have a read of the instructions!

 

Edited to add that I agree with Dave and Tony, the charging voltage is too low for modern wet batteries with lots of calcium in the plates.

Edited December 29, 2016 by nicknorman

[Ex Brummie]

You can't always get what you want, but if you try sometimes you get what you need!

Look at your expectations, look at your charging capacity. Settle for something in between.

[Rob99fla]

Thanks everyone for the help. I have had a look at the Victron manual and can see how to put it into equaliser charge. I can also set the charge voltage upon to 14.7 volts or 15 volts by DIP switches and a button. The equalisation charge increases this by 1 volt for 1 hour so I might have to do a couple of times. I will give this a try today but still have my doubts that the Halfords (read Yuasa) batteries are up to the job. I will try to get my money back as they are only 6 weeks old!! They have a 2 year warranty but last time they only replaced. I have had a look at Alpha batteries and they have a number go AGM's that will fit in my box. Some with 5 year warranty and 1000 cycles. What is the ideal charge voltage for AGM's as I can set this now I know how to. One the charger that is as the alternator is fixed at about 14.5 vols

[WotEver]

You'll need to check the spec sheet for your particular AGMs but it's generally around 14.7V. Some as low as 14.5V going up to maybe 14.8V.

[cuthound]

Which explains the sulphation/unequal cells.

 

Yes, AGMs might be a better fit for you with your low charging voltages. They can give excellent service but must be regularly fully charged as you describe because they cannot be equalised.

When I bought my boat it came with Lifeline AGM's. It still has them. The replacement cost makes my eyes water, but they are in their 11th year of service and service till have over 2/3rds of their their original capacity left.

 

They have had an easy life though, being either on float or charged by longish cruising days. According to the battery monitor, they have never been discharged below 60%.

[WotEver]

Yep, AGMs can give outstanding performance but must be well treated as there's little to nothing that can be done (with most of them) to recover abuse.

[MtB]

I will try to get my money back as they are only 6 weeks old!! They have a 2 year warranty but last time they only replaced.

 

 

I didn't realise you are already on your second set!

 

Beware of warranty replacements, the two years warranty will only be running from the purchase date of your initial set. The warranty on the new set they gave you won't be two years from the date they replaced them.

[BargeeSpud]

I too have the Victron battery monitor & I've learned to completely disregard the SOC reading. I've had a reading of 90% when my batteries have been down to 12.1V, so I now use the voltage reading to decide when I need to do a charging cycle & in my case its when the voltage drops to no lower than 12.3V to be on the safe side. I also use its amp reading to determine when I should stop charging which, with my battery capacity of 675AH, means dropping to around 9A maximum. This will give me a final percentage of 1.33%. Its only a rough guide I know, but it seems to do me OK until the Victron solar charger can do its thing properly once daylight quality gets stronger as we approach summer.

 

Anybody with any tips on how to modify or complement this regime to make it more efficient would be rather cool.

 

Have a great New Year, LL&P.

[Keith M]

As with all shunt based monitors they need to be re-synchronized 2 or 3 times a year

 

As laid out in the installation manual

 

season's greetings

Keith

[Iain_S]

As with all shunt based monitors they need to be re-synchronized 2 or 3 times a year month

 

As laid out in the installation manual

 

season's greetings

Keith

 

Fixed that for you ...

[MtB]

Out of the box my Victron BMV-702 automatically re-sets themself to 100% when the tail current falls to 4% IIRC. It can be changed but on a good set of batts 4% isn't actually fully charged so straight away it is misleading me.

[WotEver]

I too have the Victron battery monitor & I've learned to completely disregard the SOC reading. I've had a reading of 90% when my batteries have been down to 12.1V, so I now use the voltage reading to decide when I need to do a charging cycle & in my case its when the voltage drops to no lower than 12.3V to be on the safe side. I also use its amp reading to determine when I should stop charging which, with my battery capacity of 675AH, means dropping to around 9A maximum. This will give me a final percentage of 1.33%. Its only a rough guide I know, but it seems to do me OK until the Victron solar charger can do its thing properly once daylight quality gets stronger as we approach summer.

 

Anybody with any tips on how to modify or complement this regime to make it more efficient would be rather cool.

 

Have a great New Year, LL&P.

An article to confirm what you've noted about the BM: http://thunderboat.boards.net/thread/867/battery-state-charge-meters-tell

 

An article that may assist CC-ers charging with a genny: http://thunderboat.boards.net/thread/817/battery-charging-primer

[Rob99fla]

Out of the box my Victron BMV-702 automatically re-sets themself to 100% when the tail current falls to 4% IIRC. It can be changed but on a good set of batts 4% isn't actually fully charged so straight away it is misleading me.

Set mine to 1% already Mike. I think they are just rubbish batteries in the first place. Tried equaliser charge. Very hard to do as only runs fir 1 hour on the Victron. Think I need decent batteries so will try to get money back under sale of goods act. Thanks for help. Rob

Out of the box my Victron BMV-702 automatically re-sets themself to 100% when the tail current falls to 4% IIRC. It can be changed but on a good set of batts 4% isn't actually fully charged so straight away it is misleading me.

Set mine to 1% already Mike. I think they are just rubbish batteries in the first place. Tried equaliser charge. Very hard to do as only runs fir 1 hour on the Victron. Think I need decent batteries so will try to get money back under sale of goods act. Thanks for help. Rob

[Richard10002]

It's a complete minefield this battery lark

 

If you know a bit about how battery charging works, the following may help as an example of what I've learned in 10 years of screwing batteries up, and how I do it today, with my particular set up. If you dont know anything about how battery charging works, it might be gobbledegook

 

I'm off grid, so use a Honda EU20i generator via the shorepower inlet to feed a Sterling 2500W 80A 12V inverter charger and now have a 19 month old bank of 4 x Trojan T105 batteries, which are 6V 225Ah each, thus giving a total capacity at new of 450Ah at 12V.

 

I have a NASA BM2 monitor which tells me cumulative AmpHours used from the last zeroing, and instantaneous Amps out or in, (discharge of charge).

 

I also have a Smartguage monitor which gives a pretty good indication of actual State of Charge most of the time - I think it is fair to say that at the higher readings, (90% to 100%), it is not necessarily accurate, so not really a good indicator of your batteries being full.

 

The charger has a variety of settings for different battery types, so the voltage can be set at varying amounts between about 14.2V and 15.1V. It also has an equalising voltage of 15.5V, and it will run at this level for 4 hours before reverting to float voltage of about 13.5V.

 

As I understand it, when the batteries are drawing 2% capacity at a charging voltage of 14.4V, they can be considered "as good as full". I think you should also see a period where the Amps drawn doesn't fall significantly to be sure. IMHO this is the only realistic test of whether your batteries are actually as good as full.

 

NB at a voltage of say, 14.9V or 15.1V, they will obviously be drawing more than 2% capacity for the same level of charge.

 

I tend to charge at 15.1V and my charger starts at 80A bulk until the 15.1V is reached. There is then an algorithm in the charger which means that it might only charge at 15.1V for an hour, so I set a timer alarm on my phone for 50 minutes, and turn the charger off and on, until I'm happy with the days charge.

 

As the amps drawn reduces to about 10A, (450Ah nominal capacity), I change the charging voltage to 14.4V to check whether they are "as good as full". I like to get down to 1% of nominal capacity, (which might actually be 2% of actual capacity as the batteries age).

 

Once I reach "as good as full", which is usually around 5A at 14.4V, I can then stop charging, or switch to the equalising setting if I want to equalise.

 

I tend to spend 3 or 4 days a week on board, and might run the charger for a few hours at the end of the second day to top up, then I try and get to "as good as full" on the last day. If equalising, the genny could be running for 5 or 6 hours or more on the day I leave.

[Bod]

Rob

How many hours charging from the engine/generator do you do on a daily basis?

I get the feeling you may be undercharging, by relying on meters, that may not be too accurate.

Unless enough charge is replaced daily, then you will forever be buying batteries.

 

Bod

[Rob99fla]

Rob

How many hours charging from the engine/generator do you do on a daily basis?

I get the feeling you may be undercharging, by relying on meters, that may not be too accurate.

Unless enough charge is replaced daily, then you will forever be buying batteries.

 

Bod

Hi Bod. We charge every day for about 2-3 hours until tail current is stable for about an hour. Use the generator about once a week. I have just up the charge voltage to 14.7 volts from 14.4 volts. The BMV shows amps used, normally about 70 amps. Maybe it is undercharging but I'm sure the batteries are not up to it. Not sure what else to do. Can't have the engine or generator running 24/7. Need to get my money back. Was thinking of getting decent AGM's to replace. We now live as CC's so need to sort. Thanks and happy new year to you. Rob

[Keith M]

If re-sychnistion is required two or three times per month

 

To me this indicates a very poor re-charging

 

For a monitor recalculate, voltages and current have to be reached so that re-synchronise takes place

 

A Happy New Year to All

 

Keith

[BargeeSpud]

An article to confirm what you've noted about the BM: http://thunderboat.boards.net/thread/867/battery-state-charge-meters-tell

 

An article that may assist CC-ers charging with a genny: http://thunderboat.boards.net/thread/817/battery-charging-primer

 

Those are very interesting reading with some really good info, thanks.

 

My only reservation regarding genny charging with a mains charger is that in my case, my onboard genny's alternator also charges the batteries. Therefore, rightly or wrongly, I have concerns that both the alternator & mains charger both charging at the same time doesn't seem right somehow. I have the same mindset when it comes to combi inverter/chargers, it seems bizarre to me that the unit gets the batteries to charge themselves!

 

I must admit though, that if my concerns are pure rubbish (likely! ) I would definitely like to be able to do a proper charging cycle over alternator charging when my solar is restricted during winter.

Edited January 1, 2017 by BargeeSpud

[Bod]

Hi Bod. We charge every day for about 2-3 hours until tail current is stable for about an hour. Use the generator about once a week. I have just up the charge voltage to 14.7 volts from 14.4 volts. The BMV shows amps used, normally about 70 amps. Maybe it is undercharging but I'm sure the batteries are not up to it. Not sure what else to do. Can't have the engine or generator running 24/7. Need to get my money back. Was thinking of getting decent AGM's to replace. We now live as CC's so need to sort. Thanks and happy new year to you. Rob

 

How much has your charging regime altered since fitting the new fridge?

If the new fridge uses more power than the old one, then the charging time has to alter.

I fear you are relying to much on the BMV, which I believe needs recalibrating on a regular basis, to maintain any sensible level of accuracy.

Despite what some say regarding the accuracy of the last 10% of charging, the Merlin Smartguage remains the only simple accurate method of accessing the state of charge of a battery bank.

If you can afford one then great. If not then a multi-meter, with a DC clamp meter is the way to go. (NOT all clamp meters will read DC amps, beware of the real cheap ones.)

 

 

Bod

PS have a read of this thread.

http://www.canalworld.net/forums/index.php?showtopic=86831&hl=

Edited January 1, 2017 by Bod

[Rob99fla]

Hi Bod we actually replaced a 240v fridge and 240v table top freezer with a new under counter fridge, again 240v. We are using less amps per day now than before but even with tv and other stuff, the amps out per day are about 70 amps. I think it's a combination of too much load before we bought the new combined fridge/freezer, poor quality Halfords batteries and not a good enough charge regime (until now) I've upped the Victron charge voltage to 14.7 volts now and intend to charge on the gennie at least once or twice a week from now on and leave longer. Trouble is, batteries are shot. I don't think equaliser charge will work well enough. Did try it on the gennie with Victron put into equaliser mode but it only lasts one hour before reverting back to normal. If I can get my money back from Halfords (hopefully I can as on 2nd set of batteries in 3 months!), I will buy AGM's. I have considered Trojan T-105's but my battery box would need altering and don't fancy that. I have seen some ultra heavy duty AGM's but only 110ah. They weigh 34kg and have a 1000 charge cycles. Just thought better to have decent 400ah than rubbish 460ah I have now! Thanks for the link. Will read. Rob

Sorry AGM' are 100ah, not 110ah. That's what I meant

[Richard10002]

 

Despite what some say regarding the accuracy of the last 10% of charging, the Merlin Smartguage remains the only simple accurate method of accessing the state of charge of a battery bank.

If you can afford one then great.

 

There is nothing more certain than that the Smartguage WILL NOT tell you when your batteries are full. When my Smartguage shows 100% the batteries can still be drawing 20 or 30A on a nominal 450Ah bank.

 

The Smartguage does seem to give a reasonable guide as to State of Charge, once below about 80%, and is definitely good in terms of providing information related to when you need to be charging. With a separate monitor which counts cumulative AmpHours, it can also be handy in a rough calculation of remaining capacity.

 

The only thing I can see as being a simple and reasonable guide as to when batteries are as good as full is tail current at 1% to 2% of capacity, (at a charging voltage of 14.4V), and steady for a while. (There are more complicated ways of establishing that batteries are as good as full).

Edited January 1, 2017 by Richard10002

[Profzarkov]

Hi

I put a Smartgauge meter in and this has taken away a lot of the head scratching and guesswork.

I know it's deepest winter but my solar array is putting 14 amps+ into the batteries, which is nice!

[Richard10002]

Hi

I put a Smartgauge meter in and this has taken away a lot of the head scratching and guesswork.

I know it's deepest winter but my solar array is putting 14 amps+ into the batteries, which is nice!

 

Compared to not having some kind of monitor, Smartguage is a very useful tool - but please dont believe it when it tells you that your batteries are full, (100%). They might be, but they might not be.